GB2182496A

GB2182496A - Pole shoe ring for electrical machines

Info

Publication number: GB2182496A
Application number: GB08526801A
Authority: GB
Inventors: Karsten Laing
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-11-02
Filing date: 1985-10-31
Publication date: 1987-05-13
Anticipated expiration: 2005-10-31
Also published as: GB2182496B; US4593219A; GB8526801D0

Description

1 GB2182496A 1

SPECIFICATION

Pole shoe ring for electrical machines M.

k The invention refers to pole shoes for electri- 70 cal machines, in particular those having a spherical gap for the magnetic flux, in which the stator exhibits teeth which in the circum ferential direction run essentially between radii and extend through the windings.

Conventional electrical machines exhibit a cylindrical gap for the magnetic flux and are built up from sections of laminations stacked into packs. The teeth point inwards and end in pole shoes which lead to a very small clear- 80 ance between two adjacent teeth. Electrical machines having spherical gaps for the mag netic flux have independent teeth connected together by magnetic yoke packs. Their dis tance apart is at the ends pointing inwards so 85 great that pole shoe elements become neces sary in addition for widening the teeth in the region adjoining the rotor.

The idea is known, of effecting that kind of widening of teeth through soft iron profiles.

The disadvantage consists in the fact that for an electrical machine having, e.g., 36 teeth, 72 independent soft iron pieces become necessary, each of which needs fixing. The idea is further known, of arranging between the teeth and the airgap thinwalled soft iron segments. This method has the disadvantage that the magnetic flux passes perpendicularly through these soft iron segments, whereby extraordinarily heavy eddy currents are gener ated, which may dissipate up to 20% of the input power.

The invention avoids the disadvantages of both solutions. In accordance with the inven tion a closed ring is inserted, which consists of the pole shoe elements which widen the teeth, so that the flux density in the gap is reduced. Moreover it is provided that between every two of these pole shoe elements con necting straps remain through which the pole shoe elements which respectively widen one tooth become connected together mechani cally and magnetically. The magnetic flux is thereby fed from the tooth into the adjacent pole shoe elements. It is further provided that at one axial end of the ring formed from the now H-shaped elements very thin straps re main between respectively adjacent Wele ments, to which belongs only a mechanical function.

The invention is to be explained with the aid of Figures.

Figure 1 shows a motor having discrete teeth; Figure 2 shows a sector out of the motor in accordance with Fig. 1, sectioned along a plane of rotation in accordance with the line of section 11-11; Figure 3 shows the ring in accordance with the invention sectioned in side elevation; and Figure 4 shows this ring in plan.

In Figs. 1 and 2 a motor-centrifugal pump unit having a spherical gap for the magnetic flux is shown, in which the teeth (2) are formed by a plurality of laminations which run radially. For the return of the magnetic flux a spiral winding (3) is provided. Between the teeth (2) lies the winding (4). For widening the area of the teeth (2) next the rotor (6) in the circumferential direction, the soft iron regions (9) are provided. The two straps (8) respectively enclosing one tooth (2) project through the pole so that H-shaped elements are formed.

From Fig. 3 it may be seen that the Hshaped pole shoe elements of adjacent teeth, consisting of the soft iron regions (9) and the straps (8), are connected by straps (7) of the smallest possible cross-section.

Fig. 4 shows a plan of the ring in accordance with the invention, which is shown sectioned in Fig. 3. The ring is mounted on the dividing wall (12) in accordance with Fig. 1, and only after that are the teeth (2) pushed by the inwards-pointing projections (13) and (14) into the recesses (10) and (11) in the ring.

Claims

1. A pole shoe element for widening the teeth of electrical machines having discrete teeth, in particular of electric motors having a spherical gap for the magnetic flux, characterized in that each tooth (2) exhibits a groove (8a) running in the circumferential direction and that soft iron pieces (9 and 9a) serving to widen one tooth (2) are connected together by a strap (8) which passes through the groove (8a) in the tooth (2) in question and that each of the H-shaped pole shoe elements (9, 8, 9a) so formed is united into a ring with the respective adjacent H- shaped pole shoe elements by straps (7) of small cross-section, which lie at one axial end of the ring (Figs. 3 and 4).

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. Published at The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.